Method of uniform powder filling



m. W 19% EWIWN m METHOD OF UNIFORM POWDER FILLING 2 sheets shee't 1Filed Jan. 29, 1952 bbbwk INVENTORS F/amv/r 1 677 EN ,4/?7w /A 5. 714/40/ 5 BY 7% f ATTORNEY Oct. 11, 1955 F. E. STIRN ETAL METHOD OF UNIFORMPOWDER FILLING 2 Sheets-Sheet 2 Filed Jan. 29, 1952 llllll I' V IJ/VVE/VTORS FHA Mr E. sr/mv, ARTHUR s. TAYLOR,

BY 4mm; M "144M ATTORNEY METHOD OF UNIFORM POWDER FILLING Frank E. Stim,Evans Park, Pearl River, and Arthur S. Taylor, Spring Valley,N. Y.,assignors to American Cyanamid Company, New York, N. Y., a corporationof Maine Application January 29, 1952, Serial No. 268,834

1 Claim. Cl. 226-71) This present invention relates to a method offilling more nearly uniform weights of a powder whose apparent densitymay vary slightly. By compacting the powder into a standard containerand varying the vacuum slightly, it is possible to adjust the degree ofcompaction to compensate for non-homogeneity in a powder.

This application is a continuation-in-part of our copendingapplications, Serial No. 62,012 filed November 26, 1948, entitled Methodand Apparatus for Filling Powder in Capsules, and Serial No. 164,426,filed May 26, 1950, entitled Method and Apparatus for FormingCombination-Filled Capsules.

Another continuation-in-part application of Serial No. 164,426, filedMay 26, 1950, as Serial No. 399,130 has since issued as Patent No.2,697,317, December 21, 1954 entitled Capsule Forming Die Roll. Thispatent shows details of an entire encapsulation procedure in which maybe utilized the present invention.

More particularly, in filling powders by volumetric measurement, as forexample disclosed in our Patent 2,540,059, entitled Method of andApparatus for Measuring and Filling Powders Volumetrically, or infilling powders into capsules as disclosed in our co-pendingapplication, Serial No. 62,012 and our co-pending case, Serial No.164,426; there are disclosed methods for compacting a uniform powderinto charge chambers as a method of uniformly measuring a powder.Unfortunately, in filling of powders into containers or capsules, it isoften found that even though a batch of powder is uniformly blended,changes in weather conditions, or humidity, or compaction due tostanding, or electrostatic charges and other causes, causes the powderto become non-uniform, so that in the actual filling operation smallvariations occur due to non-homogeneity in the powder being filled.

We find that by varying the vacuum causing the compaction of the powderinto charge chambers, it is possible to slightly vary the charge, and byweighing occasional charges and adjusting the vacuum in accordance withthese Weight determinations, it is possible to obtain a greater degreeof uniformity than has been previously possible.

It is, of course, very preferable to use a powder of uniformcharacteristics but the characteristics of most powders to be filledwill not remain uniform over prolonged periods. Our new method ofvarying the vacuum permits adjusting the charge rapidly and readily tomaintain a high order of accuracy.

In pharmaceutical work particularly, it is highly desirable that eachindividual charge be measured as accurately as is possible. Thephysician in administering to the patient desires to know just exactlyhow much is being administered. In production, it is necessary that thecharge to each container be at least as great as the labelled weight. Tobe sure that the final containers have at least the labelled weight, itis necessary and customary to use an overage of at least three times theaverage variation in fill. In other words, if a machine will fill to anaverage variation of 2% from the mean value, it is necessary to have anoverage of at least 6% in the fill to insure that at least 99% of thecontainers have the labelled weight. It can be seen that a smallincrease in accuracy will give a disproportionately large saving in thatthe overage can be reduced and also provide a much more desirablepackage in that the superior uniformity permits a more accurateadministration to a patient.

We find that in operation, many pharmaceutical powders will vary severalpercent in apparent density. By varying the vacuum used in the apparatusof our prior inventions, above referred to, over limits in theneighborhood of from 5 to 25 inches of mercury, it is possible tocompensate for the usual changes in powder density which may beexperienced during a prolonged filling run and achieve both a saving incost of production and superior quality of product.

The exact ratio of the change of the powder charge in a standard chargechamber with a variation in vacuum will vary with the powder to befilled. However, by weighing occasional charges in the fillingoperation, it is possible to determine the direction and degree ofchange required. The relative rate of change for a given type of powderremains substantially constant.

A different calibration curve is required for each powder but may bereadily prepared in a few minutes time by an operator for the specificcharge chamber and the spe cific powder which is being used.

By way of illustration, a curve and figures for a particular powder aregiven.

Figure 1 shows a plot of the vacuum in inches of mercury against theweight of the charge in milligrams for a particular vitaminaceous powderused for filling soft gelatin capsules.

Figure 2 is a view showing a charge chamber with a forarninous area suchas may be used in practicing the present invention. Details of machinesembodying such charge chambers are embodied in our earlier applicationsof which this is a continuationin-part.

Figure 3 is a view of a powder measuring roll having therein a pluralityof charge measuring chambers, a powder containing hopper, and part of acavity die roll.

Figure 4 is a sectional view of the measuring roll along line 44 ofFigure 3.

As shown in Figure 1, measurements of the weight of a charge for aparticular vitaminaceous powder show the following:

Weight in Vacuum, inches of mercury: milligrams 4 495 A charge decreaseof 25 milligrams in the weight of the powder being filled at a vacuum of10 inches of mercury caused by non-homogeneity of the powder may becompensated by increasing the vacuum to 15 inches of mercury.

Figure 2 shows such a charge chamber 11, containing a powder charge 12.The powder charge may be drawn into the chamber by the variable vacuumacting through the foraminous area 13 through vacuum line 14. As shownin Figures 3 and 4, a machine for using the present invention includesthe measuring roll 15, which has therein a series of charge chambers 11.These charge chambers are spaced about the periphery of the measuringroll. Each charge chamber, as shown in Figure 2, may consist of atapered chamber with rounded corners and conical bottom, 16, a portionof the bottom of which is a foraminous area 13.

The foraminous area 13 should be of such porosity that the applicationtherethrough of a partial vacuum (or sub-atmospheric pressure) will suckpowder into the charge chamber compacting the powder therein, and yet besufiiciently fine in texture that the particular powder being filledwill not pack or bind into the interstices of the foraminous materialthereby unduly obstructing the flow of gases through the forarninousmaterial. pharmaceutical products, a good grade of fine felt, such as isused for wick oilers in electric motors is eminently satisfactory. Asshown in Figure 2, the foraminous area may be formed by a foraminousmaterial 17 fastened firmly into position at the bottom portion of thecharge chamber. A short threaded portion 18, with a retaining shoulder19, will serve to hold the foraminous material firmly in place. The feltmay be twisted and screwed thereinto permitting the felt to be readilyremoved and yet not permitting undue leaks around the edges. Knurled orgrooved surfaces may be used with appropriate methods of inserting thefelt, or a turned edge may be used to retain the felt. multiple partchambers may be used, wherein the felt is placed under a detachablecharge chamber so that only the working portion is exposed, or theforaminous material may consist of sintered metals, sintered glass, finemetallic screens, multiple finely spaced edges or other such material aswill suggest itself, depending upon the porosity and type of powderwhich is to be filled. The suitability of pore size may be easily testedby inserting a test portion of the material placed over a vacuum orificeinto the powder which is to be filled and then reversing the flow of gasto check and see that the material does not pack or block passages inthe material and at the same time suflicient gas is permitted to flowtherethrough to insure proper transfer and packing of the chargedmaterial.

The under-portion of the foraminous material opens on to a vacuum line14, which, as shown in Figures 3' and 4, connects to the manifoldpassages 20, which in turn lead to the respective faces of the measuringroll. Adjacent to each of the faces of the measuring roll is astationary valve plate 21. The valve plates have therein a vacuum chest22 connected to a vacuum through the vacuum connection 23; a dischargepressure chest 24 connected to a suitable source of gas pressure bypressure connection 25, and a cleaning pressure chest 26 in turnconnected to a cleaning pressure connection 2'2. The valve plates may beheld against the sides of the measuring roll by springs 28, which inturn bear against the frame or other portion of the mechanism.

A powder hopper 29 is positioned over the measuring roll 15. A powder 30is fed through the hopper into the charge chambers 11. The powder is feddown through the hopper, and by the vacuum acting through the vacuumconnection 23, and vacuum chest 22, manifold passage 20', vacuum line14, and the foraminous area 13, is compacted into the charge chamber 11,to a desired density. As each individual charge chamber passes under thefront edge of the hopper, the front edge serves as a doctor 31, to cutofi the powder charge at the level of the surface of the For many.

If desired, other retaining means such as measuring roll. The powdercharge is retained in the chamber by the vacuum until it reaches a pointin juxtaposition to powder receiving containers which may be gelatinstrip lined cavities 32 in the cavity die roll 33 at which point themanifold passage passes from its connection to the vacuum chest 22 tothe discharge pressure chest 24 through which the gas pressure actingthrough the pressure connection 25 builds up a gas pressure behind theindividual charge and uniformly and effectively forces it out of thecharge chamber into a container or capsule forming cavity 32.

A series of running checks on the weight being filled permits theoperator to vary the vacuum so as to obtain uniform charges in spite ofchanges in the apparent density of the powder. The range over whichvariations in weight may be compensated by the change in vacuum isnormally sufficiently large to compensate for any changes in a batch ofpowder that will be encountered in pharmaceutical practice.

It is convenient to. have a gauge on the vacuum line. Any standard typeof vacuum regulating device 34 may be used to control the vacuum used incompacting the powder. with or without a bleed furnishes an economicalmethod of such control. An adjustable automatic vacuum valve of any ofthe known types may be used, one such device being described in U. S.Patent 2,482,167 to Gilmont, entitled Manostat.

The size of the charge chamber may vary over a wide range depending uponthe quantity of powder which is to be filled. Either charge chambers ofvariable size, such as are disclosed in our U. S. Patent 2,540,059, ornonadjustable charge chambers as disclosed in application Serial No.62,012 and application Serial No. 164,426 may be used in the practicingof our present invention.

Having described our invention, we claim:

The method of volumetrically measuring substantially uniform chargesof aslightly non-uniform powder which comprises in succession passing aseries of charge'chambers under a powder-containing hopper, withdrawingat least a part of the gas present in the charge chambers throughforaminous material forming a part of the chamber wall by operation ofan adjustable vacuum, successively moving the charge chambers past adoctor means and ejecting the powder by means of gas pressure intosuccessive containers, determining the weight of at least some of thepowder charges and adjusting the vacuum to such a negative pressure thatthe degree of compaction of powder into the charge chamber is adjustedto compensate for non-uniformity of the powder.

References Cited in the file of this patent UNITED STATES PATENTS1,052,653 Crowley Feb. 11, 1913 2,282,477 Joa May 12, 1942 2,488,395Goldberg Nov. 15, 1949 2,540,059 Stirn et a1. Jan. 30, 1951 A needlevalve or throttling arrangement either

